For instance, as a prior art torque detection structure, which is applicable to an automotive power steering device, the torque detection structure as described in the following Patent document 1 is well known.
Briefly speaking, the prior art torque detection structure uses a torque sensor provided with a magnetic member, first and second yoke members, a pair of magnetic flux concentrators, that is, first and second magnetic concentrating members, and a magnetic sensor. A steering shaft is comprised of two shaft members connected to each other via a torsion bar such that these shaft members are rotated relative to each other. The magnetic member is connected to the outer periphery of one shaft member of the two shaft members and configured to have a plurality of magnetic poles in its circumferential direction. The first and second yoke members are a pair of annular members formed of a soft-magnetic material and connected to the outer periphery of the other shaft member of the two shaft members via a specified holder. Each of the yoke members has a plurality of radially-inward extending fingers. The yoke members are arranged to axially oppose each other. The magnetic concentrating members are partly configured within a circumferential region of respective yoke members and interposed between both the yoke members so as to axially oppose each other, for generating a magnetic field between both the yoke members. The magnetic sensor is accommodated and placed in an air gap defined between these magnetic concentrating members, for detecting a magnetic flux passing between the opposed magnetic concentrating members. The torque sensor is configured to detect, based on a change in the magnetic flux (a magnetic flux density) detected by the magnetic sensor, a torque inputted to the steering shaft.